The proposed research will track and document specific treatment-related cognitive, physiological, and behavioral changes over time in children and adolescents participating in an ongoing RCT examining the efficacy of exposure-based CBT for childhood OCD (RO1 MH58459). The primary aim of the proposed research is to develop methodology to aid in tracking the timing, sequence, and nature of these changes in order to explore such relationships in response to a standard multicomponent treatment paradigm. Specifically, participants? cognitions/irrational beliefs and physiological responses (EMG, GSR, HR) will be assessed at baseline, weeks 4, 8, and 12 of treatment, and at 6 month follow-up. Additionally, patients will complete a Behavioral Avoidance Test based on 2 symptoms from their hierarchy at baseline, post-treatment, and 6-month follow-up. An examination of each of these factors will improve upon our ability to properly assess anxiety and anxiety-related changes in youth with Obsessive Compulsive Disorder in a multimodal fashion. Moreover, the current study will enhance our knowledge of the individual effectiveness of treatment components within this population. Taking advantage of a preexisting NIMH-funded multicomponent CBT study will provide an ideal and efficient opportunity for the proposed examination. Ultimately, results will be used to support the development of prospective studies examining individual and interactive effects of cognitive and behavioral techniques with the aim of identifying mechanisms of change as well as the possible benefit of providing prescriptive treatment for this developmentally diverse population.